SEOUL – South Korea’s spy agency raided the homes and offices of a minor leftist party Wednesday and made three arrests on rare charges of seeking to start a rebellion in support of North Korea.

National Intelligence Service officers swooped on key members of the Unified Progressive Party (UPP) in Seoul, including Lee Seok-ki, a National Assembly member. Lee was not arrested because he has immunity.

The raids sparked an angry reaction from the party, which accused the conservative government of President Park Geun-hye of starting a new “Yushin dictatorship” — a reference to the authoritarian rule of her late father, Park Chung-hee.

A prosecutors’ office spokesman said three UPP members faced charges of seeking to start a rebellion and supporting North Korea in breach of the strict National Security Law.

Conservatives have accused Lee and the UPP of supporting the North Korean cause and ideology, a charge they flatly deny.

YTN television quoted an unidentified NIS official as saying that the UPP members had a plan to blow up infrastructure, including communication networks in the South, in times of a crisis with the North.